jcgam69 writes "When it was discovered in 2005, some thought Eris should be considered the 10th planet of our solar system. Everyone still considered Pluto a planet then. At first, Eris was thought to be slightly larger. Now — with the help of Eris' moon — Eris is known to be 27% more massive than Pluto. If Pluto had remained a planet to the entire community of astronomers, surely Eris would be considered the 10th planet."